System for producing and transmitting high-frequency sound energy



July 3, 192s. 1,675,879

I. B. CRANDALL SYSTEM FOR PRODUCING AND TRANSMITTING HIGH FREQUENCY SOUND ENERGY Filed Nov. 21, 1919 //1 vex Mar.- 0 1/0175. Chanda/1Patented July 3, 1928.

UNITED STATES PATENT OFFICE.

IRVING B. CRANDALL, OF EAST ORANGE, NEW JERSEY, ASSIGNOR T WESTERN ELEC-TRIO COMPANY, INCORPORATED. OF NEW YORK, N. Y., A CORPORATION OF NEWYORK.

SYSTEM PRODUCING AND TRANSMITTING HIGH-FREQUENCY SOUND ENERGY,

Application filed November 21, 1919. Serial No. 339,618.

This invention relates to systems for producing and transmitting highfrequency sound energy, and more particularly to systems for signalingor teledynamic control n which high frequency electrical energy 18 usedto produce high frequency sound energy.

An object of the invention is to provide means for producing highfrequency sound and varying it in accordance with signals or controlimpulses.

"A further object of the invention is to provide an arrangement wherebya condenser transmitter may serve to convert modulated electrical energyinto correspondingly modulated sound energy.

A feature of the invention is the provision of a vacuum tube oscillatorwith an oscillatory circuit, including a capacity element which mayserve to transmit modulated sound waves.

It has previously been proposed to produce high frequency electricalenergy, to convert said electrical energy into high frequency soundenergy, and to transmit the sound energy to a distant point where it maybe detected and utilized for signal or other teledynamic purposes.

According to the present invention a vacuum tube oscillator or othersource of high frequency electrical oscillations is associated with acondenser transmitter in such manner that modulated or otherwisemodified high frequency sounds are produced by the transmitter. Thecondenser may constitute an element of the oscillator and at the sametime serve as the modulator and sound producing device.

In the drawing, Fig. 1 illustrates an arrangement in which a condensertransmitter serves to modulate high frequency electrical energy and toproduce correspondinglymodulate'd high frequency sound energy. Fig. 2illustrates a modified system in which a condenser transmitter serves asan element of a vacuum tube oscillator and also as a high frequencysound producer. Fig. 3, il-

lustrates a further modification similar to that of Fig. 2, except thatthe space current source of the vacuum tube oscillator serves also toolarize the condenser transmitter. Fig. 4 il ustrates an additionalmodification in which the condenser transmitter serves as winding oftransformer 5.

an element of the oscillator, as a modulator and as a high frequencysound producer.

Referr1ng to Fig. 1, high frequency oscillator 1 is connected by thetransformer 2 to a. circuit including a condenser transmitter 3, atuning inductance 4 and secondary A capacitv elenent 6 shunted acrossthe secondary ivind- 111g of transformer 5 serves as a path for highfrequency current. A signaling circuit including a switch 7 is connectedto the primary winding of transformer 5 and has two branches, oneincluding a key 8 and low frequency current source-9, and the otherincluding the microphone l1 and direct current source 12, so that thiscircuit may serve for telephony, for telegraphy or for control impulsetransmission.

In operation, the circuit including condenser transmitter 3 may be tunedby inductance 4 to the frequency of the oscillations supplied by source1.

frequency oscillations from source 1 and low frequency impulses from theprimary circuit of transformer 5 are simultaneously impressed uponcondenser 3. It is well known that the attracting force between theplates of a condenser varies as the square of the impressedelectromotive force. In the case of condenser 3, the impressedelectromotive force is the sum of two alternating electrm motive forces.It is also well known that a force varying as the square of the sum oftwo harmonic,forces hasas one effective component a periodic forcehaving the frequency of the higher frequency component and having anintensity characteristic or amplitude varying in accordance with that ofthe lower frequency force. If condenser 3 be constructed so that thevarying attraction of its plates and their resulting dis placement mayset up corresponding disturbances in the surrounding medium, there willbe propagated in this medium sound waves, of the frequency of theoscillations of source 1, varying in amplitude in accordance with thelow frequency electrical impulses supplied by the primary circuit oftransformer 5. If the condenser is specially designed for submarineoperation and is placed in water, a high frequency sound If switch 7 isclosed -1n one of 1ts two positions, and the corresponding signaltransmitter is operated, high directional electromotive 'force.

wave modulated in accordance with speech, other signalingv energy, orteledynamic control impulses, as the case may be, will be transmittedthrough the water. i

In the modification of Fig. 2, as in Figs. 3 and 4, there is indicatedby heavy black lines an oscillatory circuit which serves in conjunctionwith a thermionic discharge device associated therewith as anoscillation generator. The general operation of generators of this typeis well known and will not be discussed here, except to point out thatthe oscillatory circuit or certain of its elements may serve to socouple the input and output circuits ofthe thermionic discharge deviceas to cause it to producecontinuous oscillations. As illustrated,thermionic discharge device 13 is supplied with space current by'asource 14 and has its input and output terminals connected tooscillatory circuit15 which includes a condenser transmitter 16.Theoscillator tube 13 is pro vided with a high resistance leak path 17connecting its cathode and impedance control element in well knownmanner. A high frequency retard coil 18 is provided to prevent the highfrequency energy from traversing the space current circuit. A thermionicdischarge device 19 which acts as a modulator, as will be laterexplained, has its cathode and anode connected to the same space currentsource 14. Between the discharge devices 13 and 19 and their commonsource is a reactance network comprising series inductances 20 and shuntcapacity elements 21, the function of this network being to preventripples in the unidirectional current supplied to the tubes. Lowfrequency choke coils 22 are also connected in series with source '14 tohold substantially constant the total value of the unidirection--rectifying circuit consists of a shunt thermionic rectifier element 25,and a series choke coil-26 to hold constant the rectified or uni- A-series capacity element 27 serves to-prevent the rectified electromotiveforce from being dissipated in the secondary winding of transformer 24,and a series resistance 28 may be used as a regulation device. Itisftherefore possible to polarize condenser 16 to any desired potential.Any other suitable arrangement maybe used for polarizing the condenser.

In operation, a polarized condenser transmitter transmits sound waves offrequencyand amplitude corresponding to the variable current suppliedthereto, as is Well known. Variable electromotive forces applied to theinput circuit of tube 19 correspondingly vary its in'ipcdance, and theamount of the constant current from source 14 which tube 19 diverts fromtube 13. The space current of oscillator tube 13 and the amplitude ofthe oscillations produced thereby will therefore be determined by thesignal or control circuit 29. It is therefore evident that p0- larizedtransmitter 16 will transmit high frequency sound waves of a frequencychiefly determined by the electrical constants of oscillatory circuit 15and of an amplitude determined by the variation current in circuit 29.

Referring to Fig. 3, an oscillatory circuit 30, including a condensertransmitter 31, is associated with thermionic discharge device 32 insuch manner as to constitute a generator of oscillations ofsubstantially the natural frequency of circuit 30. The space currentsource 33 is connected to discharge de vice 32 through low frequencychoke coil 34 and high frequency retard element 35 corresponding infunction to elements 22 and 18 respectively, of the system illustratedin Fig. 2. A thermionic modulator tube 36, the impedance of which iscontrolled by circuit 37, serves to determine the amplitude of theoscillations supplied to transmitter 31. Source 33 is conductivelyconnected to the terminals of transmitter 31 and serves to pclarize itdirectly, thus avoiding the necessity of a special polarizing source. i

The system shown in Fig. 4 makes use of an oscillator consisting of athermionic device 38 and-an oscillatory circuit 39 including a condensertransmitter 41. These elements and the space current supply circuit 40correspond exactly to the arran ement shown in Fig. 2. The principal dierence between this circuit and that of Fig. 2 is that condensertransmitter 41 is unpolarized;

Connected to the terminals of this condenser is a circuit 42 includingthe tuning inductance 43. An associated signal or control circuit 44serves to impress a low frequency electromotive force upon transmitter41 simultaneouslyfwiththe high frequency oscillations. As explained inconnection with the operation of the system of Fig. 1, transmitter 41will emit high frequency sound waves of a frequency determined chieflyby the electrical constants of oscillatory circuit 39 and of anamplitude determined by the signal or control currents of circuit 44.

It will, of course, be understood by those skilled in the art that thespecific circuits herein shown and described are merely illustrative ofparticular forms in which the invention may be embodied. The details ofthe circuits and the arrangements of the various elements may bematerially varied from what is set forth. The invention is therefore tobe limited only by the scope of the appended claims.

What is claimed is:

1. A condenser sound transmitter and means for applying an electromotiveforce thereto, means for simultaneously causing variations in saidapplied electromotive force at two difierent rates, and further meanswhereby the resultant sound waves reproduce the variations in theapplied electromotive force.

2. A condenser sound transmitter, means for applying thereto anelectromotive force simultaneously varying in accordance with highfrequency currents and with other lower frequency currents, whereby saidtransmitter serves to emit modulated high frequency sound waves, andfurther means whereby the resultant sound waves reproduce the variationsin the applied electromotive force.

3. An oscillator comprising a resonant 2 frequency determining circuit,and an electric discharge device having input and output circuitsconnected thereto, said resonant circuit including a condenser soundtransmitter constituting a substantial part of the capacity in saidcircuit.

4. An oscillator comprising an electric discharge device having coupledinput and output circuits, a condenser sound transmitter associated withsaid output circuit, means for supplying current. in said dischargedevice, and means for va ing said current in accordance with lowrequency impulses.

5. Means for producing modulated high frequency sound comprising acondenser sound transmitter, a vacuum tube oscillator connected thereto,and means for varying in accordance with lower frequency impulses theamplitude of the oscillations produced by said oscillator.

In witness whereof, I hereunto subscribe my name this 19th day ofNovember, A. D., 1919.

ravine B. CRANDALL.

